JPH0729859B2 - Ceramics-Metal bonding material - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a joining member of ceramics and metal.

[Technical background of the invention and its problems]

Various ceramics such as silicon nitride, silicon carbide, and alumina have been widely used as structural members and various functional members by taking advantage of their unique properties.
In many cases, the ceramic itself is used alone. If a metal can be bonded to such ceramics, it is considered that the obtained member can be used in a wider field as a member having a new function.

In the ceramic-metal joint member described above, when it is a structural part, the joint strength between the ceramic and the metal is required to be sufficiently high, while when it is a functional member, the joint interface between the ceramic and the metal is continuous. It is required to have sex. However, in general, ceramics and metals are materials with different atomic bond states,
Since chemical properties such as reactivity of the two; thermal expansion coefficient; physical properties such as electrical conductivity are different from each other, it is difficult to form a metallurgical bonding state at the bonding interface at the time of bonding the two.

By the way, conventionally, as a method for metallurgically joining ceramics and metal, the following various kinds of methods are known.

A mixture of powder containing Mo-Ti-W as a main component and an organic binder is applied to the surface of ceramics to be joined to a metal, and the mixture is heated to 1400 to 1700 ° C in a humidified atmosphere to cause a reaction, which is called metallizing. A method of forming a layer, subsequently applying Ni plating on the metallizing layer, and then joining a metal (for example, Cu base material) to the Ni plating with Pb-Sn solder or the like.

A method of joining ceramics and metal using a noble metal such as Au or Pt, that is, an alloy whose main component is a metal having a small affinity for oxygen.

A method in which an active metal such as Ti, Nb, or Zr or an active metal hydride that is converted to an active metal by heat treatment is interposed at the joint between ceramics and metal, and then the two are joined at high temperature and high pressure.

However, the above method has a drawback that it requires many steps and is complicated. Although the above method can be joined in a simple process, since an expensive precious metal is used, the economic merit is extremely small, and moreover,
High pressure is required so that the ceramic and the metal come into sufficient contact. Although the above method enables strong bonding due to the action of the active metal, it requires high bonding pressure as in the above method, and therefore is not preferably applied to parts or the like that are not susceptible to deformation.

In order to solve such problems, US Patent No. 2,857,
No. 663 discloses the following joining method. In this method, an active metal is interposed in the joint between the transition metal and the ceramic, the joint is heated to a temperature higher than the melting point of the alloy of the transition metal and the active metal and lower than the melting point of the transition metal, This is a method in which atoms are diffused into each other to form an alloy, and a transition metal and a ceramic are joined by this alloy.

However, the above method has a problem that cracks occur in the ceramic during the process of cooling the obtained ceramic-metal joint member. This is a phenomenon based on the thermal stress generated between ceramics and metal. For example, if the ceramic is alumina, silicon nitride, linear thermal expansion coefficient of each is ^{8.8 × 10 -6 /℃,2.5×10 -6 / ℃} , C
Its value is about an order of magnitude smaller than that of u, Ni, Fe, etc., and the thermal stress generated at the joint between the two becomes large. Moreover, the thermal stress increases as the difference between the temperature during joining and the temperature during cooling (room temperature) increases. Therefore, in order to reduce the thermal stress, it is required to lower the temperature at the time of joining, which requires the use of a brazing material having a low melting point at the time of joining.

In order to solve the above-mentioned problems, Japanese Patent Application Laid-Open No. 56-163093 proposes a joining method and develops a joining member constituted by diffusing a brazing material containing an active metal into both ceramics and metal. However, these methods have problems in terms of productivity and the like because complicated steps and long-time heat treatment are unavoidable, and are not always effective in relaxing thermal stress between ceramics and metal.

As a method for achieving stress relaxation when the above method is applied, a soft metal layer is interposed between ceramics and metal, and thermal stress is relaxed by its plastic deformation and elastic deformation (Japanese Patent Laid-Open No. 56-41879). ), A method of interposing a layer of a material having a coefficient of linear expansion between ceramics and metal (Japanese Patent Laid-Open No. 55-113678), and the coefficient of linear expansion changes from small to large from ceramics to metals. A method of sequentially laminating a plurality of layers and interposing them (Japanese Patent Laid-Open No. 557544)
Etc. are disclosed.

However, in the case of the above-described joining method using a brazing filler metal containing an active metal, the molten brazing filler metal often protrudes from the joint due to the pressure applied to the joint surface. If the amount of the molten brazing filler metal that has overflowed increases, cracks may occur in the ceramics due to thermal stress due to the difference in thermal expansion coefficient between the ceramics and the brazing filler metal during the process of solidifying and cooling. In order to prevent this phenomenon, it is necessary to determine the optimum amount (thickness) of the brazing filler metal that has no protrusion and is necessary for the brazing filler metal to wet the entire joint area. It is very difficult to determine the optimum amount of brazing filler metal depending on conditions such as temperature and atmosphere. Further, a method of mechanically preventing the protrusion is possible, for example, a method of sealing the outer circumference of the joint with a material having poor wettability with the brazing material, but this method makes it difficult to select a material having poor wettability. Not only that, but it also complicates the joining process, which is difficult to call a realistic method.

[Object of the Invention]

The present invention is intended to provide a ceramic-metal bonding member that has high bonding strength at high temperatures and that prevents cracking of ceramics due to thermal effects.

[Outline of Invention]

The present inventors have conducted extensive studies on a joining member in which a stress buffering member is interposed between ceramics and a metal and are wholly joined with a brazing filler metal, and as a result, a porosity of 1 to 30% by volume as a stress buffering member. As described above, the inventors have found a ceramic-metal joint member having high joint strength at high temperature and preventing cracking of ceramics due to the influence of heat, as described above.

That is, the ceramic-metal joining member according to the present invention has a metal-sintered layer having a porosity of 1 to 30% by volume on the joint surface between the ceramic and the metal, and at least between the ceramic and the metal-sintered layer. It is characterized in that they are joined with a layer containing an active metal interposed therebetween.

Examples of the ceramics include oxide ceramics such as Al ₂ O ₃ and ZrO ₂ , carbide ceramics such as SiC and TiC, and nitride ceramics such as Si ₃ N ₄ and AlN.

Examples of the metal include Fe, Ni, Co, Ti, Mo, W, Nb, Ta, Zr.
Or these alloys etc. can be mentioned.

The sintered metal layer can be obtained by a powder metallurgy method. Examples of this metal include metals having a relatively high melting point such as Ni, Co, Fe and Ti, and alloys thereof. The reason why the porosity of such a metal sintered layer is limited to the above range is that when the porosity is set to 1% by volume, the effect of relaxing thermal stress is low, cracks can be prevented, and shear strength can be improved. However, if the porosity exceeds 30% by volume, the shear strength will decrease. A more preferable porosity range is 5 to 20% by volume.

The thickness of the sintered metal layer is preferably 0.3 mm or more. The reason for this is that if the thickness of the metal sintered layer is set to 0.3 mm or less, it becomes difficult to effectively absorb the thermal stress generated between the ceramic and the metal, and the strength of the bonded portion is significantly reduced, This is because cracks may occur in the ceramics.

In such a metal sintered layer, the major contribution to the absorption of thermal stress is the absorption due to the innumerable fine pores distributed in the metal sintered layer and the plastic deformation or elastic deformation of the metal sintered layer itself. It is absorbed by. In particular, the pores in the above-mentioned sintered metal layer largely contribute to prevent the generation of cracks in the ceramics by absorbing the maximum thermal strain generated near room temperature at the time of bonding by the pores. On the other hand, the high temperature joint strength of the joint member depends on the strength of the sintered metal layer itself. Therefore, the porosity of the sintered metal layer is determined in the above range (1 to 30% by volume) in consideration of the relaxation of thermal stress and the high temperature bonding strength.

Examples of the layer containing the active metal include Ti, Nb, or Zr.
Etc. can be used in the form of foil. As the layer containing the active metal, a laminated thin film of Ti foil and Cu foil or a laminated thin film of Ti foil and Ag foil can be used.

The layer containing the active metal may be interposed between the metal sintered layer and the metal, if necessary, in addition to between the ceramics and the metal sintered layer.

Example of Invention

 Examples of the present invention will be described below.

Example 1 First, a silicon nitride cylinder having a diameter of 13 mm and a thickness of 5 mm, a diameter of 13 m
A disk of structural carbon steel (JIS, S45C) having a thickness of 5 mm and a thickness of 5 mm was prepared. Also, a Ni sintered body with a diameter of 15 mm and a thickness of 0.8 mm (density 92 to 9
3%) was prepared.

Then, between the silicon nitride cylinder and the carbon steel disk,
With a Ni sintered body interposed, a Ti layer having a thickness of 3 μm was formed between the silicon nitride cylinder and the Ni sintered body and between the Ni sintered body and the carbon steel disk.
After sandwiching the laminated thin film of foil and Cu foil, while applying a pressure of 10 kg / cm ² , hold at 5 × 10 ⁻⁵ Torr, 950 ° C. × 4 minutes, and continue cooling in argon gas. To obtain a silicon nitride-carbon steel joint member.

Shear stress was applied to the joint surface of the obtained joint member, and the shear strength from room temperature to 600 ° C. was measured. Also, as Comparative Example 1, pure Ni having a thickness of 0.8 mm was used instead of the Ni sintered plate.
A silicon nitride-carbon steel joining member was made under the same conditions as in Example 1 except that the plate was used, and the shear strength was measured in the same manner. The results are shown in the figure. In addition, A and B in the figure show the characteristic lines of the joining members of Example 1 and Comparative Example 1, respectively.

As is clear from the figure, the joining member according to the first embodiment is
It is estimated that the shear strength is 6 kg / mm ² or more from room temperature to 600 ° C., and the thermal stress between silicon nitride and carbon steel is sufficiently relaxed. On the other hand, in the case of Comparative Example 1, a shear strength of 1 to ² kg / mm ² was recognized at room temperature to 200 ° C., but cracks had already occurred in the silicon nitride of the joining member, and in the pure Ni plate It can be seen that the thermal stress is not relaxed sufficiently. The measurement itself could not be performed at 300 ° C or higher.

Example 2 First, a square silicon nitride plate having a size shown in Table 1 below and a thickness of 2 mm, and a square carbon steel plate (JIS S45C) having a size shown in Table 1 and a thickness of 10 mm were prepared. In addition, each Ni sintered plate (density 90 to 92) with the same dimensions as the silicon nitride plate and a thickness of 1.0 mm.
%) Was prepared.

Then, the Ni between each silicon nitride plate and each carbon steel plate
Sintered plates are interposed according to the size of silicon nitride, and a laminated thin film of Ti foil and Cu foil with a thickness of 3 μm is sandwiched between the silicon nitride plate and the Ni sintered plate and between the Ni sintered plate and the carbon steel plate, respectively. Then, they were treated under the same conditions as in Example 1 to obtain nine kinds of silicon nitride-carbon steel joining members.

The appearance (presence or absence of cracks in the silicon nitride plate) of each of the obtained joint members was observed. The results are also shown in Table 1 above. In Table 1, the Ni nitride-carbon steel joint member obtained by the same method as in Example 2 was used except that the Ni sintered plate was replaced by a pure Ni plate having the same dimensions as the Ni sintered plate. The appearance observation results are also shown as Comparative Example 2.

As is clear from Table 1 above, in the joining member of Example 2, cracks did not occur on the joining surface of the silicon nitride plate up to ^□ 100 mm, and the high thermal stress relaxation effect by the Ni sintered plate was recognized. On the other hand, in the case of Comparative Example 2, cracks do not occur when the bonding surface of the silicon nitride plate is only ^□ 10 mm, but cracks occur when the area is larger than that, and the thermal stress relaxation effect of the pure Ni plate is not sufficient. I understand.

When the joining member does not require shear strength at high temperature, a sintered metal layer (1 to 3) having a relatively low melting point such as Cu or Al is used.
Similar cracks can be prevented by using 0% by volume). Regarding this, a specific example will be described below.

Example 3 First, a square silicon nitride plate having a size of 2 mm and a size shown in Table 2 below and a structural carbon steel plate (JIS S45C) having a square thickness of 10 mm and a size shown in Table 2 were prepared. In addition, a Cu sintered plate (density 95 to 96) with the same dimensions as the silicon nitride plate and a thickness of 1.0 mm
%) Was prepared.

Then, the Cu between each silicon nitride plate and each carbon steel plate
Sintered plates are interposed according to the dimensions of the respective silicon nitride plates, and a 10 μm thick Ag foil and a 3 μm Ti foil are respectively placed between the silicon nitride plate and the Cu sintered plate and between the Cu sintered plate and the carbon steel plate. After sandwiching and stacking the stacked thin films of, hold at 5 × 10 ⁻⁵ Torr, 850 ° C. × 6 minutes while applying a pressure of 1 kg / cm ² , and continue cooling in argon gas to nitride 9 types. Silicon-
A carbon steel joining member was obtained.

The appearance (presence or absence of cracks in the silicon nitride plate) of each of the obtained joint members was observed. The results are also shown in Table 2 above. It should be noted that, in Table 2, a silicon nitride-obtained by the same process as the above-mentioned method except that instead of the Cu sintered plate, a phosphorus deoxidized copper plate (JIC C1221P) having the same dimensions as those Cu sintered plates was used. The appearance observation result of the carbon steel joining member is also shown as Comparative Example 3.

As is clear from Table 2 above, even if the bonding surface of the silicon nitride plate in the bonding member of this Example 3 had a large area of ^□ 150 mm, cracks did not occur, and the high stress relaxation effect of the Cu sintered plate was recognized. To be On the other hand, in the case of Comparative Example 3,
Although the bonding surface of the silicon nitride plate does not occur is seen cracks up ^□ 20 mm, it becomes a more large area, cracks.

〔The invention's effect〕

As described above in detail, according to the present invention, the bonding strength at high temperature is high, and the cracking of the ceramic due to the heat effect, especially when the bonding surface having a large area can be prevented, and thus various structural members, A highly reliable ceramic-metal joining member useful as a functional member can be provided.

[Brief description of drawings]

The drawing is a characteristic diagram obtained by measuring the shear strength by applying temperature to the joint surfaces of the silicon nitride-carbon steel joint members of Example 1 and Comparative Example 1.

 ─────────────────────────────────────────────────── --- Continuation of front page (72) Inventor Hiromitsu Takeda 1 Komukai Toshiba-cho, Sachi-ku, Kawasaki-shi, Kanagawa Inside Toshiba Research Institute, Inc. (56) Reference JP-A-58-41778 (JP, A) Kai 58-204880 (JP, A) JP 60-33269 (JP, A)

Claims (2)

[Claims] 1. A sintered metal layer having a porosity of 1 to 30% by volume is disposed on a joint surface of ceramics and a metal, and a layer containing an active metal is provided at least between the ceramics and the sintered metal layer. A ceramics-metal joining member characterized by being joined by interposing. 2. The ceramic-metal joining member according to claim 1, wherein the metal sintered layer is made of any one of Ni, Fe, Co, Ti and Zr, or an alloy thereof.